Sheet metal panel straightening device



Oct. 16', 1951 H. M. RE EVES- SHEET METAL PANEL STRAIGHTENING DEVICE Filed July 21, 1948 2 W 0 z I m a I 2 e Q4 ev-bewt' \Qeeves 57404. Pg, JAM. W

Patented Oct. 16, 1951 SHEET METAL PANEL STRAIGHTENING DEVICE Herbert M. Reeves, Kankakee, Ill., assignor to Florence Stove Company, Gardner, Mass., a corporation of Massachusetts Application July 21, 1948, Serial No. 39,959

1 Claim.

The invention relates to the manufacture of flanged sheet metal panels and more particularly to an improved method of and means for straightening panels that have become warped in the manufacturing or finishing processes.

The invention finds particular utility in the manufacture of sheet metal panels of the type used in the construction of modern cookstoves. Such panels are usually stamped or otherwise formed from flat steel sheets and are conventionally finished With a coating of vitreous enamel. In the enameling process the panels are subjected to high temperatures which frequently set up internal stresses in the metal, causing a permanent twisting or warping of the panels. Such warped panels, of course, present a very poor appearance in a stove and it has been the practice heretofore to discard them, thus substantially increasing the overall cost of production.

With the above in view, the primary object of the invention is to provide a simple and practical method, whereby such warped panels may be straightened and thus salvaged for use at a small fraction of the cost of producing the panel.

Another object is to provide a simple and inexpensive panel straightening means adapted to be permanently secured to the panel and adjusted to effectually counteract the internal stresses producing warpage of the panel.

Other objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiment illustrated in the accompanying drawing, in which;

Figure 1 is a fragmentary perspective view of j a cookstove in which sheet metal panels subject to warping are utilized as covers for the top burners.

Fig. 2 is a perspective view of a cover panel of the type shown in Fig. 1, which has become warped or twisted.

Fig. 3 is a view of the inside of the cover panel shown in Fig. 2 with the straightening means of the invention applied thereto and in process of being adjusted to straighten the panel.

Fig. 4 is a fragmentary sectional view of the cover with the straightening means applied thereto.-

Although a particular preferred embodiment of the invention has been shown and described in some detail there is no intention to thereby limit the invention to such embodiment but, on the other hand, the appended claims are intended to cover all modifications and alternative constructions within the spirit and scope of the invention as expressed in the appended claims. For purposes of illustration, the improved panel straightening method and means have been shown as applied to a sheet metal panel 5 constituting the top burner cover of a cookstove 6. The stove shown is of the table type having two groups of burners located at opposite sides of a flat generally rectangular top plate 1 upon which the covers 5 are adapted to rest when in closed position. The covers are adapted to swing open on hinge member 8 coacting with pintle brackets 9 adjacent the rear edges of the covers.

The panels 5 are alike and as shown are stamped or drawn from sheet metal to provide a generally rectangular flat top wall portion It with a continuous integral flange ll extending entirely around its marginal edge to impart stiffness to the panel and to give it a finished appearance. In this instance both sides of the panel and its flange are finished with a coating l2 of vitreous enamel. The flange II is of uniform width throughout its length so that its edges at all four sides of the panel lie in a common plane when the panel is in its normal straight or flat condition. The flanges are thus adapted to lie flush against the top plate I of the stove when the cover is closed.

As mentioned heretofore, sheet metal panels of the above general character frequently become warped due to internal stresses set up in the metal in the process of manufacture, usually in the enameling of the panel. In such cases the top wall portion l0 becomes bowed or curled, as shown in Fig. 2, and the edges of the flange H are twisted out of their normal coplanar positions.

In accordance with the invention, such warped panels are effectively straightened and thus rendered suitable for use by an improved method characterized by its simplicity and low cost. The improved method involves the permanent attachment to a flange of the panel at two points spaced apart longitudinally thereon of an adjustable member and the adjustment of that member to apply between such points a stress opposite and substantially equal to the internal stress causing the warpage of the panel.

The counter stressing member in its preferred form comprises an elongated, relatively narrow flat strip l5 of soft steel or other bendable material capable of retainin its shape against any force exerted thereon by the internal stresses in the panel. The strip I5 is formed at opposite ends with panel engaging portions l6, preferably off-set laterally from the intermediate portion I! of the strip and adapted to be rigidly secured to selected flat portions of the panel flange as by stove bolts I8. The end portions I6 are formed with flat, substantially coplanar outer faces adapted to fit tight against the panel in face-to-face relation.

The strip I5 when secured to the panel as above set forth becomes a rigid part of the panel structure. Accordingly, any distortion or bending of the strip which tends to alter the coplanar relation of the end portions I6 of the strip will set up stresses in the panel. By proper selection of the direction and extent of displacement of the end portions I6, the stresses can be applied opposite to and in an amount adapted to counteract the internal stress causing the warpage of the panel. The panel accordingly assumes a flat or straight condition.

In the illustrative application of the invention, the strip I5 is attached to the inner face of the flange I I at the hinged end of the cover panel 5. When a panel is found to be Warped beyond use, suitable holes are drilled in this flange to receive the bolts I8. As the flange is at the rear of the panel the holes are not visible from the front of the stove. The off-set construction of the strip provides clearance for the hinge member 8 and the pintle bracket 9 by which the hinge member is secured to the panel. Moreover, this off-set construction positions the intermediate portion I! of the strip conveniently for the application of suitable tools for twisting the strip to adjust the force exerted by it on the panel.

As shown in Fig. 5, the strip I5 may be adjusted by means of two simple wrench-like tools 20 adapted to grip the strip securely at suitable points spaced lengthwise thereof whereby the strip may be twisted on its longitudinal axis. The tools as shown are alike, each comprising a head portion 2| having a laterally opening slot for receiving the flat portion of the strip with a snug fit, and a handle 22 by which the head may be rocked transversely of the axis of the strip.

It will be apparent from the foregoing that the invention provides a simple, effective method and means by which warped sheet metal panels may be straightened and thus salvaged for use at very little expense. In carrying out the method to straighten the cover panel 5 of a cookstove, an adjustable counterstressing member, such as the metal strip I5, is rigidly secured to a flange of the panel, preferably at the rear or other concealed part of the panel, by means of stove bolts I8 or other suitable fasteners. The member is then adjusted manually to apply a stress to the panel in a direction and amount suflicient to counteract th internal stress causing the warpage. The adjustment comprises gripping the strip at two longitudinally spaced points and applying oppositely directed twisting forces there'- to. The extent to which the strip is permanently deformed by the twistin is determined by the amount of warpage in the panel, the twisting being interrupted when the panel becomes straight. As the strip I5 retains its twisted shape, the panel is thus permanently maintained in a fiat or straight condition.

The counterstressing member I5 utilized in the improved straightening method is simple in construction and inexpensive to produce. In its preferred form, it consists of a simple metal strip having opposite end portions I6 off-set with respect to the intermediate portion and formed with coplanar panel engaging surfaces.

I claim as my invention:

The combination with a relatively thin sheet metal panel having a coating of vitreous enamel on at least one face and subjected to warpage due to internal stresses set up in the heat treatment during enameling, of an integral flange extending around the marginal edge of the panel, an elongated flat metal strap having opposite ends, each of said'ends presenting a panel-engaging face, said faces being in a commonplane and said ends being rigidly and fixedly secured in face-to-face engagement with the inner face of the portion of said flange at the rear edge of the panel, said strap being made of steel sufficiently soft to be readily bendable but capable when bent of retaining its form against any force exerted thereon by the internal stresses in the panel, and said strap having a portion intermediate its ends offset with respect to said ends and said portion of said flange for gripping and applying to such portion a twisting force effective to permanently bend the strap in a direction to counteract the internal stress tending to warp the panel and thereby remove the warpage from the panel.

HERBERT M. REEVES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,145,608 Morton July 6, 1915 1,464,910 Landow Aug. 14, 1923 1,533,591 Hall Apr. 14, 1925 1,535,301 Francis Apr. 28, 1925 1,730,782 Reens Oct. 8, 1929 1,752,073 Foster Mar. 25, 1930 2,105,206 Stophlet Jan. 11, 1938 2,109,659 Adamson Mar. 1, 1938 2,169,198 Schweller Aug. 8, 1939 2,385,328 Whitehead 1- Nov. 30, 1943 2,335,329 Whitehead Nov. 30, 1943 2,432,563 Drake Dec. 16, 1947 2,433,272 Greiling Dec. 23, 1947 

